(;FF[4]
CA[UTF-8]
GM[1]
GN[Demo Board]
PC[https://online-go.com/review/785150]
PB[Black]
PW[White]
BR[3p]
WR[3p]
OT[Error: time control missing]
RE[?]
SZ[19]
KM[6.5]
RU[Japanese]

;AB[hr]
;AB[hq]
;AB[hp]
;AB[go]
;AB[fn]
;AB[en]
;AB[dn]
;AB[co]
;AB[bo]
;AB[ao]
;AB[ap]
;AB[cm]
;AB[hn]
;AB[jr]
;AB[eq]
;AW[gr]
;AW[gq]
;AW[gp]
;AW[fo]
;AW[eo]
;AW[do]
;AW[dp]
;AW[cp]
;AW[bp]
;AW[aq]
;AW[br]LB[fp:A]LB[cr:B]LB[dr:D]LB[fr:E]LB[gs:C]C[A - cut
B - tesuji shape
C - endgame move
D - instant life for B
E - clamp tesuji shape]
(;B[er]TR[fp]C[Correct first move, forces F4

Otherwise - if W just makes life with, say, C2, B gains 6 pts vs w 4 pts, that would be worse for W than seki]
;W[fp]
;B[cr]C[the tesuji shape I pointed out]
;W[bs]C[w makes an eye]
;B[ar]C[tesuji - removes one of w's libs in sente]
;W[bq]C[forced]
;B[fs]C[B creating eyespace with a forcing move]
;W[gs]
;B[cs]C[B makes an eye]
;W[dr]C[W reduces B's libs in sente, absolutely forcing because of the w D1 threat]
;B[dq]C[here W can choose between
F1: seki or multi-step ko (w's advantage)
D1: lose 1 pt but certain seki]
;W[fr]C[B can make simple seki]
(;B[es]C[main seki line]
;W[cq]
;B[ds]
;W[hs]
;B[is]
;W[fq]C[clearly seki]
)(;B[ds]
;W[cq]
(;B[hs]C[if B wants the multi-step ko]
;W[es]C[step ko - unlikely that B ever wins this]
;B[aa]
;W[ba]
;B[fs]
;W[bb]
;B[fq]
;W[es]
;B[ab]
;W[bc]
;B[fs]
;W[bd]
;B[ep]
;W[es]
;B[ac]
;W[be]
;B[fs]
;W[bf]
;B[as]
;W[bg]C[We can see that playing the step ko requires B to allow W 4 extra moves elsewhere.]
)(;B[es]C[B can seki anytime]
)))(;B[fp]C[Cut doesn't work]
;W[fs]
;B[fr]
;W[es]
;B[hs]
;W[gs]
;B[dr]
;W[ds]
;B[cr]
;W[cs]TR[fp]TR[eq]SQ[ar]TR[cr]TR[dr]TR[fr]C[W has at least 1 eye, B just dies]
)(;B[gs]C[INCORRECT, just saying.]
(;W[fr]
;B[er]
;W[fp]
;B[fs]LB[cr:A]LB[dr:B]LB[cs:C]LB[ds:D]C[This was my idea of reducing W

W can play A,B,C, or D to make life]
)(;W[fs]C[if w resists]
;B[fr]
;W[hs]
;B[es]
(;W[fp]
;B[gs]C[ko]
)(;W[gs]C[W cannot resist like this]
;B[fp]
;W[ep]
;B[is]
;W[fq]
;B[fp]C[just making it abundantly clear why]
))))